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	<head>
		<title>three.js webgl - particles - billboards</title>
		<meta charset="utf-8">
		<meta name="viewport" content="width=device-width, user-scalable=no, minimum-scale=1.0, maximum-scale=1.0">
		<link type="text/css" rel="stylesheet" href="main.css">
	</head>
	<body>

		<div id="info">
			<a href="https://threejs.org" target="_blank" rel="noopener">three.js</a> - webgl particle billboards example
		</div>

		<script type="importmap">
			{
				"imports": {
					"three": "../build/three.module.js",
					"three/addons/": "./jsm/"
				}
			}
		</script>

		<script type="module">

			import * as THREE from 'three';

			import Stats from 'three/addons/libs/stats.module.js';

			import { GUI } from 'three/addons/libs/lil-gui.module.min.js';

			let camera, scene, renderer, stats, material;
			let mouseX = 0, mouseY = 0;

			let windowHalfX = window.innerWidth / 2;
			let windowHalfY = window.innerHeight / 2;

			init();

			function init() {

				camera = new THREE.PerspectiveCamera( 55, window.innerWidth / window.innerHeight, 2, 2000 );
				camera.position.z = 1000;

				scene = new THREE.Scene();
				scene.fog = new THREE.FogExp2( 0x000000, 0.001 );

				const geometry = new THREE.BufferGeometry();
				const vertices = [];

				const sprite = new THREE.TextureLoader().load( 'textures/sprites/disc.png' );
				sprite.colorSpace = THREE.SRGBColorSpace;

				for ( let i = 0; i < 10000; i ++ ) {

					const x = 2000 * Math.random() - 1000;
					const y = 2000 * Math.random() - 1000;
					const z = 2000 * Math.random() - 1000;

					vertices.push( x, y, z );

				}

				geometry.setAttribute( 'position', new THREE.Float32BufferAttribute( vertices, 3 ) );

				material = new THREE.PointsMaterial( { size: 35, sizeAttenuation: true, map: sprite, alphaTest: 0.5, transparent: true } );
				material.color.setHSL( 1.0, 0.3, 0.7, THREE.SRGBColorSpace );

				const particles = new THREE.Points( geometry, material );
				scene.add( particles );

				//

				renderer = new THREE.WebGLRenderer();
				renderer.setPixelRatio( window.devicePixelRatio );
				renderer.setSize( window.innerWidth, window.innerHeight );
				renderer.setAnimationLoop( animate );
				document.body.appendChild( renderer.domElement );

				//

				stats = new Stats();
				document.body.appendChild( stats.dom );

				//

				const gui = new GUI();

				gui.add( material, 'sizeAttenuation' ).onChange( function () {

					material.needsUpdate = true;

				} );

				gui.open();

				//

				document.body.style.touchAction = 'none';
				document.body.addEventListener( 'pointermove', onPointerMove );

				//

				window.addEventListener( 'resize', onWindowResize );

			}

			function onWindowResize() {

				windowHalfX = window.innerWidth / 2;
				windowHalfY = window.innerHeight / 2;

				camera.aspect = window.innerWidth / window.innerHeight;
				camera.updateProjectionMatrix();

				renderer.setSize( window.innerWidth, window.innerHeight );

			}

			function onPointerMove( event ) {

				if ( event.isPrimary === false ) return;

				mouseX = event.clientX - windowHalfX;
				mouseY = event.clientY - windowHalfY;

			}

			//

			function animate() {

				render();
				stats.update();

			}

			function render() {

				const time = Date.now() * 0.00005;

				camera.position.x += ( mouseX - camera.position.x ) * 0.05;
				camera.position.y += ( - mouseY - camera.position.y ) * 0.05;

				camera.lookAt( scene.position );

				const h = ( 360 * ( 1.0 + time ) % 360 ) / 360;
				material.color.setHSL( h, 0.5, 0.5 );

				renderer.render( scene, camera );

			}

		</script>
	</body>
</html>
